Infrared touchscreen electronics

ABSTRACT

Touchscreen electronics for detecting touches on a display screen broadly comprises a plurality of transmitters, a plurality of receivers, and a controller. Each transmitter may transmit at least one beam across the display screen, wherein the beam may be switched on and off in a repeated pattern. The receivers may detect the beams from the transmitters, and each receiver may generate an “on” value that corresponds to the beam being switched on and an “off” value that corresponds to the beam being switched off. The controller communicates with the transmitters and the receivers and may be configured to determine that a touch has occurred when the “on” value generated by one of the receivers transitions in a sequence from greater than an upper level to less than a lower level.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of, and claims prioritybenefit to, co-pending and commonly assigned U.S. patent applicationentitled “INFRARED TOUCHSCREEN ELECTRONICS,” application Ser. No.12/787,194, filed May 25, 2010, which claims the benefit under 35 U.S.C.§119(e) of U.S. Provisional Application Ser. No. 61/250,705, filed Oct.12, 2009, entitled “INFRARED TOUCHSCREEN.” The above applications areherein incorporated by reference in their entirety.

BACKGROUND

Embodiments of the present invention relate to touchscreen displays thatutilize optoelectronic devices to detect touches on a display screen.Touchscreen displays typically include a display screen that presentsinformation to a user and touchscreen electronics for detecting toucheson the display screen. The touchscreen display may be attached to orotherwise coupled with an electronic device that performs variousfunctions and controls the information displayed on the display screen.The user may respond to questions, enter data, or otherwise operate theelectronic device by touching or physically contacting a portion of thedisplay screen.

SUMMARY

Embodiments of the present invention provide touchscreen electronics fordetecting touches on a display screen, the touchscreen electronicsbroadly comprising a plurality of transmitters, a plurality ofreceivers, and a controller. Each transmitter may transmit at least onebeam across the display screen, wherein the beam may be switched on andoff in a repeated pattern. The receivers may detect the beams from thetransmitters, and each receiver may generate an “on” value thatcorresponds to the beam being switched on and an “off” value thatcorresponds to the beam being switched off. The controller communicateswith the transmitters and the receivers and may be configured todetermine that a touch has occurred based on registering interruptedand/or uninterrupted beams. With this configuration, actual touches onthe display screen can be more accurately distinguished from “false”touches caused by excessive ambient light, debris, water spray, andother factors associated with various environments in which thetouchscreen display may be used.

This summary is provided to introduce a selection of concepts in asimplified form that are further described below in the detaileddescription. This summary is not intended to identify key features oressential features of the claimed subject matter, nor is it intended tobe used to limit the scope of the claimed subject matter.

Other aspects and advantages of the present invention will be apparentfrom the following detailed description of the embodiments and theaccompanying drawing figures.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

Embodiments of the present invention is described in detail below withreference to the attached drawing figures, wherein:

FIG. 1 is a top view of an electronic device in which the touchscreenelectronics configured in accordance with various embodiments of thepresent invention may be implemented;

FIG. 2 is a top view of the electronic device with a front cover removedto show the transmitters and receivers of the touchscreen electronicspositioned adjacent to the edges of a display screen;

FIG. 3 is a schematic sectional view of the touchscreen display showingthe transmitters and receivers positioned at the edge of the displayscreen and underneath the front cover of the electronic device;

FIG. 4 is a block diagram of the electronic device and the touchscreenelectronics in accordance with various embodiments of the presentinvention;

FIG. 5 is a schematic view of the display screen, the transmitters, andthe receivers depicting a beam pattern created by the touchscreenelectronics;

FIG. 6 is a schematic view of the beam pattern created by a prior artarray of transmitters and receivers;

FIG. 7 is a plot of a transmit signal and a beam of one of thetransmitters vs. time;

FIG. 8 is a plot of a receive signal of one of the receivers vs. timedepicting a touch on the display screen;

FIG. 9 is a plot of the receive signal vs. time depicting the presenceof infrared radiation near the receiver;

FIG. 10 is a schematic view of the display screen, the transmitters, andthe receivers depicting a touch on the display screen;

FIG. 11 is a schematic view of the display screen, the transmitters, andthe receivers depicting a pinch or an unpinch on the display screen; and

FIG. 12 is a flow diagram of at least a portion of the steps of a methodfor establishing operating parameters for the touchscreen display.

The drawing figures do not limit the present invention to the specificembodiments disclosed and described herein. The drawings are notnecessarily to scale, emphasis instead being placed upon clearlyillustrating the principles of the invention.

DETAILED DESCRIPTION

The following detailed description of the invention references theaccompanying drawings that illustrate specific embodiments in which theinvention can be practiced. The embodiments are intended to describeaspects of the invention in sufficient detail to enable those skilled inthe art to practice the invention. Other embodiments can be utilized andchanges can be made without departing from the scope of the presentinvention. The following detailed description is, therefore, not to betaken in a limiting sense. The scope of the present invention is definedonly by the appended claims, along with the full scope of equivalents towhich such claims are entitled.

In this description, references to “one embodiment”, “an embodiment”, or“embodiments” mean that the feature or features being referred to areincluded in at least one embodiment of the technology. Separatereferences to “one embodiment”, “an embodiment”, or “embodiments” inthis description do not necessarily refer to the same embodiment and arealso not mutually exclusive unless so stated and/or except as will bereadily apparent to those skilled in the art from the description. Forexample, a feature, structure, act, etc. described in one embodiment mayalso be included in other embodiments, but is not necessarily included.Thus, the present technology can include a variety of combinationsand/or integrations of the embodiments described herein.

Various embodiments of the present invention may include a touchscreendisplay for use with an electronic device. The touchscreen displaybroadly comprises a display screen and touchscreen electronics fordetecting touches on the display screen. The touchscreen electronics maycomprise a plurality of transmitters, a plurality of receivers, and acontroller. Each of the transmitters may be configured to transmit abeam across the display screen, wherein the beam may be switched on andoff in a regular pattern. Each of the receivers may receive the beamfrom at least one of the transmitters and may be operable to generate an“on” value that corresponds to the beam being switched on and an “off”value that corresponds to the beam being switched off. In variousembodiments, the transmitters may be configured to transmit and thereceivers may be configured to receive infrared (IR) wavelength beams.The controller may communicate with the transmitters and receivers andmay be configured to determine that a touch has occurred based onregistering interrupted and/or uninterrupted beams.

In some embodiments, the transmitters are placed along all sides of thedisplay screen. The receivers are placed along the sides of the displayscreen, generally interleaved with the transmitters, such that onereceiver is positioned between two transmitters. During operation, eachtransmitter transmits a beam that is received by a portion of thereceivers. Thus, a pattern of crisscrossing beams is created close tothe surface of the display screen. When a user touches the displayscreen, a portion of the beams is broken. “Touch,” as utilized herein,refers to a user physically contacting the display screen with his orher finger or another object and/or placing his or her finger or anotherobject in close proximity to the display screen without physicallycontacting the display screen. As a result of a touch, the receivers onone or more sides of the display screen no longer receive thetransmitted signals. The touchscreen electronics may use the location ofthe inactive receivers to determine the coordinates of the point ofdisplay screen contact.

The touchscreen display may be utilized in a variety of environments andthus may encounter various situational problems. For example, in amarine environment, the touchscreen display may be exposed to steam,mist, or water spray. In colder environments, condensation or frost mayform on the display screen. In any environment, including aviationenvironments, the touchscreen display may encounter sunlight, smoke, orliquid spills, while debris, dust, dirt, sand, or other objects maycollect on the display screen. All of these factors may adversely affectthe performance of conventional touchscreen displays, either by creatingfalse touches on the display screen or by preventing the ability todetect an actual touch.

Embodiments of the technology will now be described in more detail withreference to the drawing figures. Referring initially to FIG. 1, anelectronic device 10 in which the touchscreen display 12 of the presentinvention may be integrated is illustrated. Embodiments of thetouchscreen display 12 may comprise a display screen 14 and touchscreenelectronics 16. As described in more detail below, the touchscreenelectronics 16 may broadly comprise a plurality of transmitters 18, aplurality of receivers 20, and a controller 22, as seen in FIG. 4.

The electronic device 10 may be any device that presents visualinformation to a user and with which the user may interact. Examples ofthe electronic device 10 include commercial, retail, or publicinformation kiosks located in banks, shopping malls, airports, and thelike, computing devices such as a desktop computer or a laptop computer,medical test or diagnostic equipment used in a hospital or laboratory,navigation and instrumentation equipment used in an aircraft, marinevessel, or automobile, and similar electronic components.

The electronic device 10 may include components not necessarily shown inthe figures, such as inputs, outputs, and communication ports. Inputsmay include knobs, dials, switches, keypads, keyboards, mice, joysticks,combinations thereof, and the like. Outputs may include audio speakers,lights, dials, meters, printers, combinations thereof, and the like.Communication ports may be wired or wireless, electronic, optical, radiofrequency (RF), combinations thereof, and the like.

The electronic device 10 may also include a processing element 23 thatperforms logical functions and controls the information and data that isdisplayed on the display screen 14. The information and data displayedmay depend on computer programs, software, or code that is executed bythe electronic device 10, input from users utilizing the inputsdiscussed above, input from the touchscreen electronics 16 of thecurrent invention generated from users touching the display screen 14,and combinations thereof. The processing element 23 may includemicroprocessors, microcontrollers, or similar components that arecapable of executing computer programs, software, or code. Theprocessing element 23 may further include data storage components suchas read-only memory (ROM), random-access memory (RAM), hard-disk drives,optical disk drives, flash memory drives, combinations thereof, and thelike.

The electronic device 10 may further include a cover 24 that is shown inFIG. 1, but is removed in FIG. 2 to reveal the transmitters 18 and thereceivers 20. The cover 24 generally provides protection for thetransmitters 18, the receivers 20, the display screen 14, and any othercomponents in the vicinity thereof. In some embodiments, the cover 24may include or form a bezel. The cover 24 may have a shape that conformsto a housing or a body of the electronic device 10 to which the cover 24may be attached. The cover 24 may include a window 26 or opening thataligns with the display screen 14. The window 26 may have a similar sizeand aspect ratio as the display screen 14. In order to accommodate theoperation of the transmitters 18 and the receivers 20, the cover 24 maybe shaped so that the window 26 does not contact the display screen 14and allows some space therebetween. In some embodiments, the spacebetween the window 26 and the display screen 14 may be empty. In otherembodiments, there may be a transparent gasket or seal between thewindow 26 and the display screen 14. Furthermore, when the touchscreendisplay 12 is finally assembled, the cover 24 may be positioned over thetransmitters 18 and the receivers 20, as seen in FIG. 3. Accordingly,the user may not be able to see or access the transmitters 18 and thereceivers 20.

The display screen 14 may display information or data encouraging theuser to interact with the electronic device 10. The information mayinclude questions or statements that prompt the user to touch thedisplay screen 14. The information may also include on-screen keyboards,numeric or alphanumeric keypads, menuing systems, popup windows, and thelike. Thus, the user may touch the display screen 14 to respond toprompts or questions, type text, enter numbers, activate menus, openwindows or dialog boxes, scroll through lists, or similar activities.Thus, the electronic device 10 may be controlled by or may operate inresponse to touches on the display screen 14.

The display screen 14 may be of a variety of types, including, but notlimited to, a cathode ray tube (CRT), plasma, light-emitting diode(LED), organic LED (OLED), LEP (Light Emitting Polymer) or PLED (PolymerLED), liquid crystal display (LCD), thin film transistor (TFT) LCD, LEDside-lit or back-lit LCD, combinations thereof, and the like. In variousembodiments, the display screen 14 may be integral with the electronicdevice 10, as shown in FIGS. 2-3 and exemplified by a device such as amulti-use avionics-system controller. In other embodiments, the displayscreen 14 may be separate from the electronic device 10, such as with acomputer monitor or other video monitor.

The display screen 14 is generally flat to accommodate the operation ofthe touchscreen electronics 16, as discussed in more detail below. Thedisplay screen 14 may have multiple sides but is typically four-sidedwith a top side 28, a bottom side 30, a left side 32, and a right side34. The display screen 14 may possess a square or a rectangular aspectratio and may be viewed in either a landscape or a portrait mode.

The transmitters 18, also designated as “TX”, and the receivers 20, alsodesignated as “RX”, may be positioned along one or more sides of theperimeter of the display screen 14 as seen in FIGS. 2, 5, and 10-11 suchthat the transmitters 18 may transmit beams 36 across the display screen14 to the receivers 20, as shown in FIGS. 3 and 5. Typically, thetransmitters 18 and the receivers 20 are placed such that they areadjacent to the entire perimeter of the display screen 14. Accordingly,the number of transmitters 18 and receivers 20 may depend on themagnitude of the perimeter, the size of each transmitter 18 and receiver20, and the space between each device. Other factors may influence thenumber of transmitters 18 and receivers 20, such as minimizing powerconsumption of the touchscreen display 12, in which case the number oftransmitter 18 and receivers 20 may be reduced.

Generally, the transmitters 18 and the receivers 20 are placed with thetransmitters 18 being interleaved with the receivers 20, such that onereceiver 20 is positioned between two transmitters 18 and vice versa.The beam 36 from the transmitter 18 may have a conical shape in generalor a triangular shape when viewed in a plane. Thus, the beam 36 from onetransmitter 18 may reach several receivers 20 on the other side of thedisplay screen 14. As a result, several beams 36 may be formed betweenone transmitter 18 and the receivers 20 on the opposing side. Forexample, as seen in FIG. 5, one beam 36 may be formed between onetransmitter 18 and each of four receivers 20 to produce a total of fourbeams 36, although this number may decrease near the corners of thedisplay screen 14. Furthermore, each receiver 20 may receive a beam 36from multiple transmitters 18. Hence, there may be multiple beams 36that lead to one receiver 20. For example, as seen in FIG. 5, eachreceiver 20 may receive four beams 36, except in the vicinity of thecorners of the display screen 14 where the number of beams 36 perreceiver 20 decreases.

In various embodiments, the transmitters 18 may be positioned along oneside of the display screen 14 substantially linearly aligned with thetransmitters 18 along the opposite side of the display screen 14.Likewise, the receivers 20 may be substantially linearly aligned withreceivers 20 along opposing sides of the display screen 14. Thisorientation may produce the pattern of beams 36 shown in FIG. 5, and maybe contrasted with prior art transmitter 18 and receiver 20 orientationswherein the transmitters 18 may be substantially linearly aligned withthe receivers 20 along opposing sides of the display screen 14, whichproduces the pattern of beams 36 shown in FIG. 6. Aligning thetransmitters 18 with other transmitters 18 and the receivers 20 withother receivers 20 generally provides better coverage of the displayscreen 14 with the beams 36 such that there are smaller areas where nobeams are present as compared with the prior art.

Each of the transmitters 18 generally transmits a beam 36 thatcorresponds to a transmit signal 38 from the controller 22. The transmitsignal 38 may be received by a transmitter input 40. Each transmitter 18may receive the transmit signal 38, either as a voltage or a current,from the controller 22 and generate the corresponding beam 36 with anintensity that is proportional to the magnitude of the transmit signal38—typically in the infrared (IR) wavelength range of approximately 700nanometers (nm) to approximately 1500 nm. The beam 36 may be consideredto be an optical transmission and thus the transmitter 18 may includelight-emitting diodes (LEDs), surface-emitting or edge-emitting lasers,similar optoelectronic devices, or combinations thereof.

The transmit signal 38 from the controller 22 may be a binary squarewave signal that includes a zero portion and a one portion, designatedas “0” and “1”, respectively, in FIG. 7, wherein the transmit signal 38oscillates between zero and one at a given frequency. The zero portionof the transmit signal 38 may be a zero amplitude or near-zero amplitudevalue. The one portion of the transmit signal 38 may be a high amplitudevalue.

Accordingly, the behavior of the beam 36 may follow the waveform of thetransmit signal 38, as shown in FIG. 7. Typically, the beam 36 is offduring the zero portion of the transmit signal 38. In some embodiments,the beam 36 may have a very low intensity during the zero portion. And,the beam 36 may be on or radiating during the one portion of thetransmit signal 38 at a higher intensity proportional to the value ofthe transmit signal 38. Thus, the beam 36 may be switched on and off atthe frequency of the transmit signal 38.

Each of the receivers 20 may produce a receive signal 42 that iscommunicated through a receiver output 44 and corresponds to radiationdetected by a sensing surface of the receiver 20. The receiver 20 mayinclude photodetectors, photocells, phototransistors, photoresistors,photodiodes, other photosensitive materials that may detect IRradiation, or combinations thereof. The receiver 20 may produce thereceive signal 42 as an analog electrical or electronic output, eithervoltage or current, that corresponds to the detected radiation.

The receive signal 42 may include a zero portion and a one portion thatcorrespond to the zero portion and the one portion of the transmitsignal 38, generally shown in FIG. 8. During the zero portion of thereceive signal 42, the receiver 20 may generate an off value thatcorresponds to the beam 36 being off. During the one portion of thereceive signal 42, the receiver 20 may generate an on value thatcorresponds to the beam 36 being on. The level of the zero value may bezero or nearly zero, and the level of the one value may be proportionalto the intensity of the beam 36 that impacts the receiver 20. However,when the beam 36 is interrupted or broken by the user during the act oftouching the display screen 14, the on value of the receive signal 42may be significantly reduced in amplitude to zero or near zero. Thus,during the time in which the user is touching the display screen 14 andthe beam 36 is interrupted, both the off value and the on value of thereceive signal 42 may have a zero or near-zero amplitude value.

Furthermore, since the receive signal 42 generally corresponds to theradiation that strikes the receiver 20, the receive signal 42 mayinclude the waveform of the beam 36 as well as the characteristics ofany ambient radiation that may be present in the surroundings of thetouchscreen display 12. For example, sunlight is often present in theenvironments where touchscreen displays 12 are implemented, such as thecockpit of an aircraft, wherein it may also be difficult to preventsunlight from shining on the touchscreen display 12—particularly at lowangles. When sunlight shines on the display screen 14, it may alsocontact at least a portion of the receivers 20. Sunlight typicallyincludes a sufficient amount of IR radiation to affect the receivesignal 42 and may provide a constant IR input to the receiver 20, whicheffectively raises the floor of the receive signal 42 waveform.Therefore, in the presence of sunlight, the amplitude of the off valueof the receive signal 42 may increase to a higher level, as shown inFIG. 9.

The controller 22 may include digital to analog converters (DACs),analog to digital converters (ADCs), signal amplifiers, drivers, similarelectrical or electronic circuits, or combinations thereof. Thecontroller 22 generally sends the transmit signal 38 to the transmitters18 and receives the receive signal 42 from the receivers 20.Accordingly, the controller 22 may include a plurality of outputs 46that are coupled to the transmitter inputs 40 and a plurality of inputs48 that are coupled to the receiver outputs 44. The transmit signal 38and the receive signal 42 may include a variable analog voltage orcurrent level.

The controller 22 may also include a data output 50 to send informationto the electronic device 10, such as the location on the display screen14 where a touch occurred. In order to determine the location of a touchand perform other functions, the controller 22 may execute computerprograms, software, code, instructions, algorithms, or firmware, andcombinations thereof. The controller 22 may include hardware thatautomatically performs instructions, such as finite state machines(FSMs). The controller 22 may also include microprocessors,microcontrollers, field-programmable gate arrays (FPGAs),application-specific integrated circuits (ASICs), combinations thereof,and the like, and may be implemented using hardware descriptionlanguages (HDLs), such as Verilog and VHDL. The controller 22 mayfurther include data storage components such as read-only memory (ROM),random-access memory (RAM), hard-disk drives, optical disk drives, flashmemory drives, combinations thereof, and the like. In addition, thecontroller 22 may include communication ports to allow for programmingor other miscellaneous functions.

The touchscreen display 12 may function as follows. The controller 22may send the transmit signal 38 to a first transmitter 18A, which may beany of the transmitters 18. For ease of understanding, the firsttransmitter 18A may be located near a corner of the display screen 14.The transmit signal 38 may be a square wave with a zero portion and aone portion, as seen in FIG. 7, wherein the controller 22 sets the valueof the transmit signal 38 during both the zero portion and the oneportion. During the zero portion, the value of the transmit signal 38may be zero or approximately zero in order to turn the first transmitter18A off. During the one portion, the transmit signal 38 may be set to avalue to drive the transmitter 18A to produce an intensity of the beam36 that can easily be detected by the receivers 20.

The beam 36 transmitted by the first transmitter 18A may be received bymultiple receivers 20 on the opposing side of the display screen 14, ineffect creating multiple beams 36—one beam 36 for each receiver 20. Anexemplary pattern of beams 36 created by the transmitters 18 and thereceivers 20 is shown in FIG. 5. As can be seen, the number of beams 36between a transmitter 18 and multiple receivers 20 depends primarily onthe location of the transmitter 18.

For each receiver 20 that receives a beam 36 from the first transmitter18A, the controller 22 checks the receive signal 42 generated by thegiven receiver 20. As discussed in more detail below, if the on value ofthe receive signal 42 is greater than an upper break band 52 and the offvalue of the receive signal 42 is less than a lower break band 54, thenit is likely that the beam 36 is uninterrupted and that nothing istouching the display screen 14 along the path of the given beam 36. Thecontroller 22 checks the receive signal 42 of the next receiver 20 toreceive a beam 36 from the first transmitter 18A. If the off value andthe on value of the receive signal 42 are within acceptable parameters,then the controller 22 checks the next receiver 20 to receive a beam 36from the first transmitter 18. In a likewise fashion, the controller 22checks all the receive signals 42 of the receivers 20 receiving the beam36 from the first transmitter 18A. If the receive signals 42 are allacceptable, then the controller 22 sends a transmit signal 38 to asecond transmitter 18B.

The controller 22 then checks the receive signals 42 of all thereceivers 20 receiving the beam 36 from the second transmitter 18B. Thecontroller 22 continues to send a transmit signal 38 to each transmitter18 in a serial fashion and check the receive signals 42 from thecorresponding receivers 20. The process continues until an event occurs,as described below.

In certain situations, the value of the receive signal 42 may not fallwithin acceptable limits. For example, when the touchscreen display 12is exposed to direct sunlight or other sources of IR radiation, the offvalue of the receive signal 42 may rise or increase. Alternatively, theintensity of the beam 36 produced by a given transmitter 18 may vary dueto process variations in the manufacture of the transmitters 18, suchthat for the same value of input in the transmit signal 38, sometransmitters 18 may generate a beam 36 with a lower intensity.Consequently, the on value of the receive signal 42 may be reduced aswell. These changes in the levels of the signal 42 may lead to errors inperformance of the touchscreen display 12, wherein the controller 22 mayfalsely determine that a touch has occurred when nothing has contactedthe display screen 14 or may not detect a touch when a user has touchedthe display screen 14.

In order to tolerate changes in the expected levels of the receivesignal 42, the controller 22 compares the values of the receive signal42 to the upper break band 52 and the lower break band 54, as seen inFIGS. 8-9. The upper break band 52 may be a number above which the onvalue of the receive signal 42 is acceptable. Thus, the receiver 20 isproperly receiving the beam 36 from the transmitter 18. The lower breakband 54 may be a number below which the off value of the receive signal42 is acceptable. In other words, the output of the receiver 20indicates that the beam 36 is off when it should be off. The range ofvalues between the upper break band 52 and the lower break band 54 maybe a break band 56. Values of the receive signal 42 that are in thebreak band 56 may be considered indeterminate.

The levels of the upper break band 52 and the lower break band 54 may beset by the manufacturer after assembly of the touchscreen display 12.The value of the upper break band 52 may be set by recording the onvalue of each receive signal 42 for each beam 36 with none of the beams36 being interrupted. The upper break band 52 value may be set to lessthan the smallest on value of the receive signal 42 for all the beams36. The setting of the upper break band 52 increases the tolerance ofthe touchscreen display 12 to variations in the performance of thetransmitters 18. The value of the lower break band 54 may be set byexposing the touchscreen display 12 to a source of IR radiation, such assunlight, and recording the off value of the receive signal 42 for eachbeam 36 when all of the beams 36 are blocked. Alternatively, the valueof the receive signal 42 for each beam 36 may be recorded when all thetransmitters 18 are off and no beams 36 are transmitted. The lower breakband 54 value may be set to greater than the highest off value of thereceive signal 42 for all the beams 36. The setting of the lower breakband 54 increases the tolerance of the touchscreen display 12 to theeffects of sunlight or other IR radiation sources.

When a user touches the display screen 14, at least two touch events mayoccur. The first touch event may include the user placing his finger ora pointing object, such as a stylus, on the display screen 14. Thesecond touch event may include the user removing his finger or thepointing object from the display screen 14.

When the first touch event occurs, one or more beams 36 may beinterrupted. When a beam 36 is interrupted, the on value of the receivesignal 42 from the corresponding receiver 20 may be reduced to zero ornear zero, which is typically below the lower break band 54. Since thereceive signal 42 is normally a square wave when the corresponding beam36 is uninterrupted, the controller 22 expects that the on value of thereceive signal 42 should be above the upper break band 52. Thus, thecontroller 22 may determine or register that a beam 36 has beeninterrupted, signifying that a touch may have been initiated and that atouch event has occurred, when the on value of the receive signal 42 isbelow the lower break band 54, as shown in the middle portion of FIG. 8.The initiation of a touch may also be known as a downstroke. It ispossible that the on value of the receive signal 42 may not transitionto below the lower break band 54 in one cycle, or in other words, thebeam 36 may not be fully blocked by the user's touch in one cycle. Itmay take a few cycles for the transition to occur, during which time theon value of the receive signal 42 may gradually decrease through thebreak band 56, as seen in the left portion of FIG. 8. The controller 22may be implemented or programmed to allow for the gradual decrease ofthe receive signal 42 over a few cycles. However, if the receive signal42 when the beam 36 is on takes an excessive amount of time totransition, during which the value of the receive signal 42 is in thebreak band 56, then the controller 22 may determine that there is aproblem with the beam 36, as discussed below.

The on value of the receive signal 42 may remain below the lower breakband 54 while the user is touching the display screen 14 andinterrupting the corresponding beam 36. When the user lifts his fingerfrom the display screen 14, or terminates the touch, the beam 36 may nolonger be interrupted. As a result, the on value of the receive signal42 may increase and transition to be greater than the upper break band52, and the controller 22 may determine or register that the beam 36 isno longer interrupted and has been restored, signifying that the touchhas been terminated and a touch event has occurred. The termination of atouch may also be known as an upstroke. Like the downstroke, theupstroke may occur over a number of cycles of the square wave of thereceive signal 42. Hence, the on value of the receive signal 42 maygradually increase during a few cycles, as seen in the right portion ofFIG. 8.

When the controller 22 determines that a beam 36 has been interrupted,the controller 22 continues to check the values of other receive signals42 for indications of interrupted beams 36, as typically a touchinterrupts a plurality of beams 36. The beams 36 may include X beams 58and Y beams 60. The X beams 58 may travel roughly horizontally and maybe transmitted by transmitters 18 positioned adjacent to the left side32 and the right side 34 of the display screen 14. The Y beams 60 maytravel roughly vertically and may be transmitted by transmitters 18positioned adjacent to the top side 28 and the bottom side 30 of thedisplay screen 14. To determine that the interruption of a plurality ofbeams 36 is a valid touch, the controller 22 checks for at least oneinterrupted beam 36 in a first direction and at least two interruptedbeams 36 in the orthogonal direction. Thus, the controller 22 determinesthe downstroke is valid when there are at least two X beams 58 and one Ybeam 60 that are interrupted or at least two Y beams 60 and one X beam58 that are interrupted.

FIG. 10 depicts an actual touch 62 on the display screen 14 from theuser's fingertip, for example, as well as a calculated touch 64 and thebeams 36 that are interrupted by the fingertip. One possible approach todetermining the calculated touch 64 may be to average the locations ofthe intersections of the beams 36. However, as can be seen, some of thelocations where X beams 58 intersect with X beams 58 and Y beams 60intersect with Y beams 60 are located at a distance away from the actualtouch 62. Including these intersections in the computation of thecalculated touch 64 may lead to inaccuracies and additional calculationtime. Thus, the controller 22 includes only the locations of theintersections of X beams 58 with Y beams 60 in computing the calculatedtouch 64. In various embodiments, the calculated touch 64 may becalculated as the average of the points where the X beams 58 intersectwith the Y beams 60. Once determined, the calculated touch 64 may becommunicated to the electronic device 10 through the data output 50.

Once the controller 22 has determined that a valid downstroke hasoccurred, the controller 22 may develop a list of beams 36 that havebeen interrupted. Since the controller 22 considers only theintersection of X beams 58 with Y beams 60 in computing the calculatedtouch 64, then the controller 22 must ascertain the coordinates of eachX beam 58-Y beam 60 intersection. One approach to determining the X beam58-Y beam 60 intersection points may be to calculate the intersectiongiven the path of each beam 36. However, this approach may requireexcessive processing time for each occurrence of a touch. Instead, giventhat the positions of the transmitters 18 and the receivers 20 are fixedand the trajectories of the beams 36 do not change, the controller 22may calculate the X beam 58-Y beam 60 intersection points just once whenthe touchscreen display 12 starts up. The controller 22 may then storethe intersection points in a lookup table memory element internal to thecontroller 22. Thereafter, the controller 22 may simply retrieve theintersection points from the memory element when computing thecalculated touch 64.

During the normal operation of the touchscreen display 12, it ispossible for environmental factors to impact the performance of thedisplay 12. In certain environments, frost crystals may develop on thedisplay screen 14. The growth of the crystals may be slow, and as thefrost is developing, it may not fully block any of the beams 36, butrather one or more of the beams 36 may be partially blocked, therebyreducing the intensity of the beams 36 that strikes the receivers 20. Asa result, the on value of the receive signal 42 may decrease slowly overtime until the value is in the break band 56, where it may remain for along period of time. During a valid touch, the on value of the receivesignal 42 may transition from greater than the upper break band 52through the break band 56 to less than the lower break band 54.Typically, however, the transition occurs within a few cycles of thesquare wave from the transmitter 18. Thus, the controller 22 may assumethat there is a problem if the on value of the receive signal 42 is inthe break band 56 for more than a few cycles. If the on value of thereceive signal 42 remains in the break band 56 for greater than apredetermined period of time, then the controller 22 may consider thecorresponding beam 36 to be inoperable and may remove the beam 36 fromconsideration when computing the next calculated touch 64. Thepredetermined period of time may be given as a certain number of cyclesof the square wave, or it may be given as an absolute quantity of timesuch as 5 seconds.

Other factors that may affect the performance of the touchscreen display12 include smoke in the vicinity of the display screen 14, dust thatcollects on the display screen 14, water or other liquids that land onthe display screen 14, or similar objects that may contact the displayscreen 14 and remain there. Objects such as these may fully or at leastmostly block one or more beams 36 for an extended period oftime—typically longer than the time for a valid touch to occur. Thus,the controller 22 may determine that a downstroke has occurred whilewaiting for the upstroke to occur. In this instance, the on value of thereceive signal 42 may be less than the lower break band 54 for anextended period of time. If the on value of the receive signal 42 isless than the lower break band 54 for an extended period of time, thenthe controller 22 may consider the corresponding beam 36 to beinoperable due to debris on the display screen 14 and may remove thebeam 36 from consideration when computing the next calculated touch 64.The predetermined period of time may be given as a certain number ofcycles of the square wave, or it may be given as an absolute quantity oftime such as 5 seconds.

In various configurations, the controller 22 may register an interruptedbeam when the on value generated by one of the receivers 20 transitionsin a sequence from greater than the lower break band 54 to less than thelower break band 54, register an uninterrupted beam when the on valuegenerated by one of the receivers 20 transitions in a sequence from lessthan the upper break band 52 to greater than the upper break band 52,and determine that a touch event has occurred based on at least one ofthe registered interrupted beam and the registered uninterrupted beam.

In some configurations, the controller 22 may determine that a touch hasbeen initiated when the on value generated by one of the receivers 20transitions from greater than the upper break band 52 to less than thelower break band 54 and determine that a touch has been terminated whenthe on value generated by one of the receivers 20 transitions from lessthan the lower break band 54 to greater than the upper break band 52.

There may be some situations in which the on value of the receive signal42 for a given beam 36 is less than the lower break band 54 for anextended period of time while there is no debris on the display screen14. For instance, the user may drag his finger on the display screen 14along the path of one or more beams 36 in order to perform an actionsuch as scrolling through a list. Usually, during the process, new beams36 are interrupted that cross the path in which the user is dragging hisfinger. In the case of contaminants on the display screen 14, no newbeams 36 are interrupted other than those that were originally broken bythe debris.

When considering whether a beam 36 is inoperable due to debris on thedisplay screen 14, the controller 22 may check for other beams 36 beinginterrupted during a predetermined window of time. The window may begiven as a certain number of cycles of the square wave, or it may begiven as an absolute quantity of time. Hence, the controller 22 mayconsider a beam 36 to be inoperable due to debris on the display screen14 only if no new beams 36 are interrupted during the window of time.Accordingly, the controller 22 may determine that a drag is occurring ifmultiple beams 36 are interrupted in succession over a short period oftime. The controller 22 may interpret the events as a downstrokefollowed by a drag followed by an upstroke.

There may be additional events which can affect the performance of thetouchscreen display 12. For example, a liquid spill may interrupt alarge percentage of beams 36, as might large objects coming into contactwith the display screen 14, such as sheets of paper or plastic orarticles of clothing, the user's hand accidentally touching the displayscreen 14, and the like. Thus, if the controller 22 detects that thenumber of beams 36 that are interrupted at a given time exceeds apredetermined amount, then the controller 22 determine that a spill or alarge contact event has occurred and the controller 22 may send a signalto the electronic device 10 that there is a problem with the displayscreen 14. The predetermined amount of beams 36 may be established byallowing a small number of people to touch the display screen 14 andrecording the number of beams 36 that are interrupted by each touch. Thepredetermined amount of beams 36 may equal the largest number of beams36 interrupted plus an optional safety value that may be a percentage ofthe largest number.

Events or circumstances that affect the performance of the touchscreendisplay 12, such as debris or objects on the display screen 14, aretypically not permanent. Frost and liquids may evaporate. Other debrismay be removed or the display screen 14 may be cleaned. Once any of thebeams 36 has been determined to be stuck in the break band 56 orinoperable due to debris on the display screen 14 or other factors, thecontroller 22 may monitor the receive signal 42 for the associated beams36 to check for a return to normal behavior. The controller 22 maydetermine that a beam 36, previously identified as inoperable, is normalwhen the on value of the corresponding receive signal 42 is greater thanthe upper break band 52 for a certain number of cycles. An exemplarynumber of cycles may be approximately twelve.

In order to perform certain functions of the electronic device 10, suchas zooming in or out of an image displayed on the display screen 14, theuser may apply a pinching gesture by touching the display screen 14typically with the thumb and index finger spaced apart and subsequentlyjoining the two together. Additionally, the user may apply an unpinchinggesture by touching the display screen 14 typically with the thumb andindex finger joined together and subsequently spacing the two apart.FIG. 11 depicts a thumb touch 66 and a finger touch 68 on the displayscreen 14 along with the beams 36 that are interrupted by the touches66, 68. The controller 22 may define a bounding box 70 from the extentsof the intersections of X beams 58 with Y beams 60 for both the thumbtouch 66 and the finger touch 68. From the coordinates of the boundingbox 70, the controller 22 may calculate an area of the box 70. If thearea of the bounding box 70 increases over time, then the controller 22may determine that an unpinch is occurring, as the user spreads histhumb and finger apart. If the area of the bounding box 70 decreasesover time, then the controller 22 may determine that a pinch isoccurring, as the user moves his thumb and finger closer to one another.

In various embodiments, the controller 22 may be able to adjust theperformance or the specifications of the transmitters 18 and thereceivers 20. For example, the output power of the transmitter 18 andthe sensitivity of the receiver 20 may be adjusted. Each transmitter 18and receiver 20 may include one or more programmable potentiometerswhich may be used to adjust settings of the transmitter 18 and thereceiver 20, such as the gain of amplifiers included in both thetransmitter 18 and the receiver 20. It is possible that the touchscreendisplay 12 may be able to overcome the effects of frost on the displayscreen 14 by increasing the output power of the relevant transmitters 18such that the receivers 20 may detect the beam 36 in spite of the frost.

At least a portion of the steps of a method 100 for establishingoperating parameters for a touchscreen display 12 is listed in FIG. 12.The steps may be performed in the order as shown in FIG. 12, or they maybe performed in a different order. Furthermore, some steps may beperformed concurrently as opposed to sequentially.

In connection with step 101, a plurality of transmitters 18 and aplurality of receivers 20 are placed around the edges of a displayscreen 14. The transmitters 18 and the receivers 20 may be positionedsuch that each transmitter 18 is generally opposing one or morereceivers 20.

In connection with step 102, a beam 36 that is modulated on and off istransmitted between a plurality of transmitter 18 and receiver 20 pairs.Each transmitter 18 transmits the beam 36 to at least one receiver 20.The beam 36 may be turned on and off in a square wave fashion.

In connection with step 103, an output of each receiver 20 is recordedwhen the beam 36 is on in order to collect a plurality of beam 36 onvalues. Each receiver 20 may generate a receive signal 42, which is anelectrical or electronic output that corresponds to the intensity of thebeam 36 that contacts the receiver 20. The on value of the receivesignal 42 may have a high amplitude value.

In connection with step 104, the receivers 20 are exposed to a source ofinfrared (IR) radiation. Sunlight may include IR radiation. Thus, thetouchscreen display 12 may be placed in direct sunlight.

In connection with step 105, the output of each receiver 20 is recordedwhen the beam 36 is off in order to collect a plurality of beam 36 offvalues. The off value of the receive signal 42 may normally beapproximately zero. However, in the presence of sunlight, the off valueof the receive signal 42 may be greater than zero.

In connection with step 106, an upper break band 52 is set to less thanthe lowest beam 36 on value. The upper break band 52 may be set to belower than the weakest transmitter 18 output.

In connection with step 107, a lower break band 54 is set to greaterthan the largest beam 36 off value. The lower break band 54 may be setto be higher than the level of unwanted input from sunlight.

The above-described touchscreen display 12 provides numerous advantagesover prior art touchscreen displays. For example, the touchscreendisplay 12 may reduce the occurrence of false touches caused by debrison the display screen 14 by recognizing that one or more beams 36 havebeen interrupted for a period of time that exceeds a threshold. Thetouchscreen display 12 may function properly in the presence of sunlightby compensating for the unwanted IR input to the receivers 20. Thetouchscreen display 12 may determine that a spill has occurred byrecognizing that the number of beams 36 that are interrupted exceeds athreshold. The touchscreen display 12 may determine that frost isdeveloping on the display screen 14 by recognizing that one or morebeams 36 is partially blocked. The touchscreen display 12 may determinethat a pinch or an unpinch is occurring on the display screen 14 bymonitoring the size of a bounding box of beams 36 that are interrupted.

Although the invention has been described with reference to theembodiments illustrated in the attached drawing figures, it is notedthat equivalents may be employed and substitutions made herein withoutdeparting from the scope of the invention as recited in the claims.

Having thus described various embodiments of the invention, what isclaimed as new and desired to be protected by Letters Patent includesthe following:
 1. An electronic device comprising: a display screen;touchscreen electronics comprising a plurality of transmitters operableto transmit beams across the display screen and a plurality of receiversoperable receive the transmitted beams; and a controller incommunication with the transmitters and the receivers and configured to—detect broken beams utilizing signals provided by the receivers,identify one or more intersections of the detected broken beams, definea bounding box using one or more of the intersections of the brokenbeams, determine an area of the bounding box, and determine that a pinchgesture is being performed if the area of the bounding box increasesover time.
 2. The device of claim 1, wherein the controller isconfigured to determine that an unpinch gesture is being performed ifthe area of the bounding box decreases over time.
 3. The device of claim1, wherein the identified intersections include one or moreintersections of broken X beams with broken Y beams.
 4. The device ofclaim 3, wherein the controller is configured to define the bounding boxfrom the extents of the intersections of broken X beams with broken Ybeams.
 5. The device of claim 1, further comprising a processing elementoperable to perform logical functions associated with the electronicdevice.
 6. The device of claim 5, wherein the processing element isoperable to utilize the determined pinch gesture as a user input.
 7. Thedevice of claim 5, wherein the controller is integrated with theprocessing element.
 8. An electronic device comprising: a displayscreen; touchscreen electronics comprising— a plurality of transmitterspositioned adjacent to opposing sides of the display screen fortransmitting beams across the display screen, each beam being switchedon and off in a repeated pattern, a plurality of receivers positionedadjacent to opposing sides of the display screen for detecting the beamsfrom the transmitters, each receiver operable to generate an on valuethat corresponds to the beam being switched on and an off value thatcorresponds to the beam being switched off; and a controller incommunication with the transmitters and the receivers and configured to—identify a first touch position and a second touch position utilizing atleast the off value generated by one or more receivers, define abounding box using the first touch position and second touch position,determine an area of the bounding box, and determine that a pinchgesture is being performed if the area of the bounding box increasesover time.
 9. The device of claim 8, wherein the controller isconfigured to determine that an unpinch gesture is being performed ifthe area of the bounding box decreases over time.
 10. The device ofclaim 8, wherein the controller is configured to determine the touchpositions by calculating the points where an interrupted beamtransmitted from one side of the display screen intersects aninterrupted beam transmitted from an orthogonal side of the displayscreen.
 11. The device of claim 10, wherein the controller is configuredto determine the extents of one or more intersections of interrupted Xbeams with interrupted Y beams corresponding to the determined touchpositions.
 12. The device of claim 11, wherein the controller isconfigured to define the bounding box from the extents of theintersections of interrupted X beams with interrupted Y beams.
 13. Thedevice of claim 8, further comprising a processing element operable toperform logical functions associated with the electronic device.
 14. Thedevice of claim 13, wherein the processing element is operable toutilize the determined pinch gesture as a user input.
 15. The device ofclaim 13, wherein the controller is integrated with the processingelement.
 16. An electronic device comprising: a display screen;touchscreen electronics comprising— a plurality of transmitterspositioned adjacent to opposing sides of the display screen fortransmitting beams across the display screen, each beam being switchedon and off in a repeated pattern, a plurality of receivers positionedadjacent to opposing sides of the display screen for detecting the beamsfrom the transmitters, each receiver operable to generate an on valuethat corresponds to the beam being switched on and an off value thatcorresponds to the beam being switched off; and a controller incommunication with the transmitters and the receivers and configured to—identify a first touch position and a second touch position by utilizingat least the off values provided by the receivers to calculate thepoints where an interrupted beam transmitted from one side of thedisplay screen intersects an interrupted beam transmitted from anorthogonal side of the display screen, determine the extents of one ormore intersections of X beams with Y beams corresponding to thedetermined touch positions, define a bounding box using the extents ofthe intersections of X beams with Y beams, determine an area of thebounding box, and determine that a pinch gesture is being performed ifthe area of the bounding box increases over time.
 17. The device ofclaim 16, wherein the controller is configured to determine that anunpinch gesture is being performed if the area of the bounding boxdecreases over time.
 18. The device of claim 16, further comprising aprocessing element operable to perform logical functions associated withthe electronic device.
 19. The device of claim 18, wherein theprocessing element is operable to utilize the determined pinch gestureas a user input.
 20. The device of claim 18, wherein the controller isintegrated with the processing element.